Automated adaptive muscle stimulation method and apparatus

ABSTRACT

An automated adaptive muscle stimulation system and method are disclosed. The stimulation system includes at least one electrode assembly adapted to deliver a muscle stimulation signal to the tissue of a user, a sensor system adapted to detect a muscle response, and an electrical stimulation device operably coupled to the at least on electrode assembly and the sensor system, the electrical stimulation device including a control system operable to automatically diagnose at least one characteristic of a muscle from the detected muscle response and adjust at least one parameter of the muscle stimulation signal in response thereto to deliver an adjusted muscle stimulation signal. A dual mode muscle stimulation system adapted to accept first and second data sets and provide first and second levels of treatment data is also disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/321,691, filed Jan. 23, 2009, which is a continuation of U.S. patentapplication Ser. No. 11/046,524, filed Jan. 28, 2005, claims the benefitof U.S. Provisional Application No. 60/540,871, filed Jan. 30, 2004,each of which is incorporated herein in its entirety by reference. Anyand all applications for which a foreign or domestic priority claim areidentified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

FIELD OF THE INVENTION

The present invention relates generally to electro-stimulation. Moreparticularly, the present invention is directed to an apparatus andmethod for automated adaptive muscle stimulation wherein the musclestimulation may be adjusted by a measured muscle reaction.

BACKGROUND OF THE INVENTION

It is common practice for therapists, physicians, athletes, and otherindividuals to utilize various treatment and therapy devices to promotemuscle training, conditioning, and growth. In addition, devices oftenreferred to as Transcutaneous Nerve Stimulation (“TENS”) units areemployed to manage pain and discomfort through blocking of the nervesignal from the area of discomfort to the brain. With muscle stimulationand nerve stimulation, a device is programmed to output various levelsof electrical pulses. The frequency, duration, pulse width, andintensity of the output signal control the directed treatment goals.

With regard to muscle stimulation, there are a myriad of uses for theseelectro-stimulation devices. Treatment categories can generally bedivided between muscle fitness, muscle aesthetic, sport training, painmanagement, muscle rehabilitation, and vascular therapy. Each categoryis directed to a different stimulation goal. With muscle fitness, thegoal is generally to restore, improve, or maintain a good physicalcondition by building muscle, muscle tone, volume, trophism, metabolism,and the like. With muscle aesthetic goals, the stimulator is oftenutilized on muscles in order to shape, firm, refine, increaseelasticity, and increase caloric expenditure. Sports-minded individualsmay use the device to increase muscular endurance and strength, increaseblood flow to promote active recovery, and the like. When focus is onmuscle rehabilitation, muscular stimulation is needed to restore orotherwise redevelop a convalescent muscle. Under the vascular categoryof treatment programs, the goal is to improve blood circulation in thestimulated area to minimize circulatory problems, fatigue, lack ofoxygenation, swelling, and other related problems. In pain managementapplications, electro-stimulation devices are used primarily toalleviate muscle pain or other discomfort.

Regardless of the unique goal-dependent outputs of the device,electro-stimulation works under a principle of voluntary musclecontraction. When individuals contract a muscle, the brain sends theinformation to the muscle via the motor nerve. With electro-stimulation,a suitable electric current acts directly on the nerve by means ofelectrical impulses that reproduce the natural physiological phenomenon.These electrical impulses are applied to the user through attachedelectrodes. The electrodes are typically adhesively attached to theperson or person's clothing. With electro-stimulation a patient or usercan achieve intensive muscular work without mental or cardiac fatigue,thus reducing joint and tendon constraints. U.S. Pat. No. 6,324,432,commonly assigned with the present application to Compex SA, disclosesan electrical neuromuscular stimulator for measuring muscle responses toelectrical stimulation pulses, and U.S. Patent Application PublicationNo. 2003/0074037 discloses an electrical nerve stimulation device. U.S.Pat. No. 6,324,432 and U.S. Patent Application Publication No.2003/0074037 are incorporated by reference herein in their entireties.

However, conventional electro-stimulation devices, while useful inachieving intensive muscular work for a target or generalized muscleset, are not capable of self-adjusting for various muscle groups.Conventional devices are also not capable of automatically adjusting forvarious users; even though two patients may be seeking the same generaltherapeutic or training effects, each may be at a different fitness orrecovery stage. Further, conventional electro-stimulation devices arenot generally able to self-adjust for detected physiological traits of aparticular user.

Conventional devices also frequently require application and supervisionby a trained medical professional to prevent muscle over-stimulation,fatigue, or, in extreme situations, injury. Additionally,electro-stimulation treatment delivered by conventional devices istypically less efficient because theses devices are unable to consideror account for muscle feedback. As a muscle is stimulated, it may reactor respond in a manner for which adjustment of the stimulation isappropriate. For example, a fatigue level experienced by a muscle variesand generally accelerates as treatment progresses. Fatigue levelsexperienced and the acceleration of fatigue will be different for eachuser and each target muscle or group and must be carefully monitored toincrease the efficiency of electro-stimulation in sports applications.

Monitoring muscle response and feedback directly is difficult andimpractical in most treatment situations as such monitoring is mosteffectively accomplished by subcutaneous sensors. While transcutaneousapplications of accelerometers or other devices are known,electro-stimulation devices presently available cannot accurately andactively self-adjust a treatment session based on detected feedback.Further, the measurements are often inaccurate because of interferencefrom other active but non-target muscles.

U.S. Pat. No. 4,817,628 discloses a system and method for evaluatingneurological function controlling muscular. movements. The systemgenerally includes an accelerometer sensor, a stimulus electrodeassembly, and a portable device to which the sensor and electrodeassembly are connected. The sensor measures the magnitude of the(stimulus evoked) movement of a body part of the subject along at leastone axis of three-dimensional space.

U.S. Pat. No. 6,282,448 discloses a self-applied and self-adjustingdevice and method for prevention of deep vein thrombosis with movementdetection. An accelerometer can detect motion and keep the deviceoperating until motion is generated and/or tum the device off whenmotion is detected, generated by the device or user.

U.S. Patent Application Publication No. 2002/0165590 discloses anapparatus for stimulating a muscle of a subject. An accelerometer may beemployed that is positioned adjacent a muscle of the subject that isbeing stimulated. This meter then tracks the magnitude of the shiversgenerated in the muscle. If this magnitude exceeds a predeterminedlevel, the apparatus is notified and may be adjusted or shut off.

Additionally, Tarata et al. discuss general approaches used to monitormuscle fatigue in “The Accelerometer MMG Measurement Approach, inMonitoring the Muscular Fatigue,” from the MEASUREMENT SCIENCE REVIEW,Vol. 1, No. 1, 2001, and in “Mechanomyography versus Electromyography,in monitoring the muscular fatigue,” from BIOMEDICAL ENGINEERING ONLINE,published Feb. 11, 2003. McLean provides a mechanomyography summary in asubject message “MMG summary” posted to a Biomechanics and MovementScience listserver on Mar. 30, 1998. The above articles are incorporatedby reference herein in their entireties.

The need remains, however, for an electrical muscle stimulation deviceand corresponding electrode system that substantially addresses theinnate drawbacks of conventional devices and systems.

SUMMARY OF THE INVENTION

The present invention solves many of the above described deficienciesand drawbacks inherent to conventional electro-stimulation devices andtreatments. In particular, the invention provides for intelligent musclestimulation by an automated adaptive muscle stimulation system capableof adjusting stimulation parameters to user physiology, therebyenhancing user comfort, and improving treatment efficiency. Thisintelligent muscle stimulation system is non-invasive and can be used intandem with other exercise or activity, thereby facilitating theintegration of electrotherapy into a wider variety of treatmentprotocols. During use of the muscle stimulation system, the stimulationenergy may be continuously monitored, verified, and adjusted. The systemprevents the onset of detrimental muscle contractions and customizestreatment based upon muscle feedback and user physiology. Musclefatigue, for example, can be one focus of the muscle feedback.

An automated adaptive muscle stimulation system in accordance with oneembodiment of the invention includes at least one electrode assembly, asensor system, and an electrical stimulation device. The electricalstimulation device includes a control system operable to automaticallydiagnose at least one characteristic of a muscle from a detected muscleresponse and adjust at least one parameter of the muscle stimulationsignal in response thereto to deliver an adjusted muscle stimulationsignal. The electrode assembly is operably coupled to the electricalstimulation device and is adapted to deliver a muscle stimulation signalto the tissue of a user. In one embodiment, the electrode assembly isadapted to be placed on or around a designated or predetermined bodypart or muscle to bring the electrode into contact with a user's skin orthe clothing proximate a user's skin to deliver electrical stimulationsignals via the stimulation system and detect muscle reactions andresponses via the sensor system.

The above summary of the invention is not intended to describe eachillustrated embodiment or every implementation of the invention. Thefigures and the detailed description that follow more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a top view of an electrical stimulation device in accordancewith one embodiment of the invention.

FIG. 2 is a schematic block diagram of an electrical stimulation devicein accordance with one embodiment of the invention.

FIG. 3 is block diagram of an electrical stimulation device inaccordance with one embodiment of the invention.

FIG. 4 is a schematic of an accelerometer circuit in accordance with oneembodiment of the electrical stimulation device of the invention.

FIG. 5 is an exemplary graph depicting a chronaxia point m accordancewith one embodiment of the invention.

FIG. 6 is an exemplary energy measurement scale graph m accordance withone embodiment of the invention.

FIG. 7 is an energy graph according to one embodiment of the invention.

FIG. 8 is a current graph according to one embodiment of the invention.

FIG. 9 is a pulse width graph according to one embodiment of theinvention.

FIG. 10 depicts principles of fatigue measurement according to oneembodiment of the invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The adaptive muscle stimulation system and method of the inventionprovide intelligent muscle stimulation, wherein the stimulation can beadjusted by a detected muscle response, and wherein the stimulator canbe used by non-medical personnel. The invention can be more readilyunderstood by reference to FIGS. 1-10 and the following description.While the invention is not necessarily limited to such an application,the invention will be better appreciated using a discussion of exemplaryembodiments in specific contexts.

Herein throughout, the term “user” will be used to refer generally topatients or persons receiving electro-therapy and electrostimulationtreatments. The term “operator” will be used to refer generally todoctors, nurses, therapists, and other medical professionals, as wellsupervisory personnel and those having specialized or particulartraining relating to the use of electro-therapy devices.

Referring to FIGS. 1 and 2, a muscle stimulation system 10 according toone embodiment of the invention includes an electrical stimulationdevice 12, an electrode interface 14, and at least one electrodeassembly 16. Electrode assembly 16 can include a muscle intelligence(MI) sensor system 17 or a plurality of MI sensor systems 17. MI sensorsystem 17 includes a sensor device, for example an accelerometer, fordetecting a muscle reaction or response to an applied electrostimulationsignal. Sensor system 17 will be described in more detail below.

In one embodiment, electrical stimulation device 12 comprises a unithousing 20; a user interface system having an input portion 24 and anoutput portion 23; a control system 40 (refer also to FIG. 3); and aplurality of output channels 28. Input portion 24 includes a pluralityof keys or buttons in communication with control system 40 to providemenu support and selection options prior to, during, and after runningof the stimulation routines. Output portion 23 includes a visual displayportion 22 and, in one embodiment, an auditory output portion, forexample a small external or enclosed speaker or the like (not shown).

Referring to FIG. 3, one embodiment of control system 40 comprises asignal conditioning portion 42 effecting signal amplification andfiltration, a multiplexer portion 44, and a microcontroller 46. Controlsystem 40 is preferably programmable such that a treatment orstimulation program created, designated, or prescribed by an operatorcan be stored in microcontroller 46 and subsequently selected by theuser to initiate a stimulation routine based upon individual needs andcharacteristics inputted via input portion 24. Control system 40 can beequipped with pre-programmed stimulation routines, or the routines canbe selectively programmed based upon the device assignment to aparticular user and according to his or her individual needs. Access tocontrol system 40 can also be password protected or otherwise programmedto provide a first level of access to users for input of a first set ofuser-specified information and data and select stimulation programs andcharacteristics from those available via input portion 24 and outputportion 23, and a second level of access providing programmingcapabilities, maximum and minimum stimulation parameter selection, andother operations reserved for operators such as trainers, doctors,nurses, therapists, and other medical professionals, also via inputportion 24 and output portion 23.

Control system 40 is operable to control generation of electricalstimulation signals, or pulses, and subsequent delivery of thestimulation signals to a user by at least one electrode assembly 16.Based upon the desired stimulation treatment program and goals for theuser as input by the user and programmed by the operator, control system40 automatically controls and maintains the appropriate stimulationprogram(s) and signal characteristics.

Electrode interface 14 provides connectivity between control system 40and electrode assembly 16 via output channels 28. In one embodiment,each electrode assembly 16 includes a connector 30 adapted to coupleelectrode assembly 16 to an output channel 28 at interface 14 and acable 32. Cable 32 provides limited local separation of device 12 andelectrode 16, permitting user movement during treatment and convenientstorage of device 12 during use, for example in a pocket or on a beltclip or the like.

Each electrode assembly 16 includes at least one electrode 17 adaptedfor application to a user's tissue. In one embodiment, electrode 17 is aflexible structure having an adhesive on at least one side adapted fordirect contact with a user's skin for application of stimulation signalsto a user's tissue. In another embodiment, electrode 17 is a flexiblestructure mounted on a belt or band for application of stimulationsignals to a user's tissue directly or through the user's clothing.Electrodes 17 can be applied to almost any targeted nerves, muscles, ormuscle groups. For instance, electrode assembly 16 can provideelectrical stimulation to the following muscles or muscle regions:stomach; abdominals; quads; calves; certain chest, thoracic, andshoulder muscles; cervical region; lumbar region; buttocks; biceps;feet; and thighs. Other regions and muscles can be targeted due to theflexible configuration options of electrodes 16 without deviating fromthe spirit and scope of the invention, while other regions shouldpresently be avoided, including the cardiac and proximate regions,because of the risk of inducing cardiac fibrillation.

The invention further comprises a muscle intelligence (MI) system thatmakes it possible to diagnose, transcribe, and automatically adaptcertain stimulation parameters to suit a particular user's physiologyand muscle reactions. The MI system permits users to safely customizeand adjust a muscle stimulation treatment or workout session to theirindividual needs, physiological characteristics, and muscle reactions,instead of being restricted to general factory pre-set defaultparameters. The MI sensor also provides measurement and analysis ofcertain physiological characteristics of the muscle in order to adaptthe related stimulation parameters accordingly. The MI system is enabledprimarily via an MI sensor system, or a plurality of MI sensor systems,in communication with electrical stimulation device 12 and controlsystem 40. In one embodiment, the MI sensor system is incorporated intoat least one electrode assembly 16 and forms an interactive link betweenthe muscles being treated and stimulator 12.

Referring to FIG. 2, at least one MI sensor 50 is coupled to an outputchannel 28 of stimulator 12 at interface 14, replacing any one of thestandard, non-MI electrodes. In one embodiment, a plurality of MIsensors 50 can be used. An electrode assembly 16 incorporating MI sensor50 thereby includes a sensor system and a stimulation system and servesa dual function, operating as both a sensor that diagnoses the muscleand a standard electrode that provides stimulation, whether one MIsensor 50 or a plurality of MI sensors 50 are used in a particulartreatment session.

In one embodiment, sensor system 50 comprises an accelerometer device 52operable to measure and monitor muscle reaction during a treatmentsession. More specifically, accelerometer device 52 is operable todetect an onset, a modification, or a disappearance of a muscle responsein reaction to a stimulation signal applied to the muscle by stimulationdevice 12. In other representative embodiments, sensor system 50 cancomprise a tension strain gauge, a measurement detector, or anothersensor device known to those skilled in the art.

In use, after a stimulation signal is delivered to a muscle by MI sensor50, one of several things will occur. First, if the stimulation signalis too small, i.e., the current is too low, to stimulate the muscle tocontract, the muscle will not react and no response will be detected byaccelerometer device 52. Second, if the stimulation signal is highenough to stimulate the muscle, the muscle will react to some degree anda mechanical response will be detected by accelerometer device 52.Third, if the muscle is already contracted when a stimulation signal isapplied, the muscle may still react at some level detectable byaccelerometer device 52, or the muscle will not react because it haspeaked, in which case accelerometer device 52 will detect no reaction orwill detect a disappearance of a muscle reaction. In any of thesesituations, if the muscle reacts with either a slight twitch or agreater degree of contraction, accelerometer device 52 is operable todetect the mechanical response very quickly in the form of a reactionpulse.

In one embodiment, accelerometer device 52 detects a series of reactionpulses m response to a succession of electrical pulse signals deliveredto the muscle by stimulation device 12 and communicates the detectedpulses to control system 40. Control system 40 records the shapes of theseries of reaction pulses detected and calculates a coefficient ofcorrelation of the reaction pulses. This process is then repeated forsubsequent pulse and reaction sequences and the series of calculatedcoefficients of correlation is compared.

For example, a series of stimulation pulses is applied to a particularmuscle via electrode(s) 16 and subsequent muscle reactions are detectedby accelerometer device 52 included within at least one electrode 16.The correlation coefficient between each of the muscle reaction signalsis stored by control system 40 and compared with the other responsesignals. The amplitude of the correlation coefficients is recorded andchanges in one coefficient from another coefficient enable controlsystem 40 to detect either an apparition of a muscle response to theelectrical pulses or a modification of the muscle state, for example acontraction of the muscle. The correlation coefficients can also becomputed using an algorithm during the program duration to obtain otherinformation about the particular muscle state.

Accelerometer device 52, or a plurality of accelerometer devices 52, canbe utilized in the manner described herein in cooperation with aplurality of treatment modes to customize device 12 for any user'sunique physiology, target muscle or muscles, and treatment goals. Thecustomization can be based solely upon information provided by a user,information programmed or provided by an operator, or preferably uponinformation from both a user and an operator. An exemplary circuitschematic in accordance with one embodiment of accelerometer device 52of the invention is shown in FIG. 4

Exemplary stimulator treatment modes and applications that canimplemented by system 10 in cooperation with electrode 17, MI sensor 50,and accelerometer device 52 are described in further detail below.

MI-Scan

The muscle intelligence scan (MI-scan) function adapts an electricalmuscle stimulation session to the physiology of a particular user. Justprior to beginning a stimulation session, system 10, via control system40, electrode assembly 16, and sensor system 50, scans and measures theexcitability of the target muscle group and automatically adjusts therelevant stimulator parameters to the excitability of the target musclegroup. The resulting measurement is user-customized. The MI-scanfunction is accessible by all programs involving a muscular contraction,and therefore also requiring electrical stimulation pulse widthadjustment, of the target muscle or muscles, particularly those programsrequiring the choice of a muscle group.

The MI-scan function allows a user to adapt the characteristics of thestimulation signals and pulses to the individual specificities of eachuser and the excitability characteristics of the stimulated muscle,i.e., a muscle chronaxia. Referring to FIG. 5, the rheobase, Rh, is theminimum intensity necessary to stimulate a muscle with an infiniteimpulse duration:

Rh=i

Muscle chronaxia is a characteristic applied pulse duration required toachieve optimum stimulation of a particular muscle at an intensity thatis twice the rheobase, or 2 Rh. Muscle chronaxia is dependent upon theparticular muscle group and subject, according to Lapicque's Law:

${I = {\frac{q}{t} + i}},$

wherein I is the intensity of a stimulation current; q is anexperimentally determined coefficient that corresponds to a certainquantity of electrical charges; t is an impulse duration; and i is acurrent intensity. A conventional muscle stimulator uses rectangularimpulses with a fixed pulse width. Therefore, in these systems, thecurrent output is adjusted through the intensity. For instance, arectangular impulse of 200 microseconds (μS) would have a pulse widthwith an adjustable intensity setting between 0 and 100 mAmp.

According to principles of electro-physiology, the optimal pulse widthis equal to or approximates the chronaxia of the target motomeurons,which results in more comfort and a more specific excitement of thetarget motomeurons. Because the pulse width may vary from a first targetmuscle to another target muscle, using the intensity as a scale ofcurrent output is not reliable. Nevertheless, as conventional musclestimulators are not equipped with a chronaxia measurement system, thesestimulators must use a fixed pulse width that is not optimum.

Control system 40, in communication with the sensor system 50 andaccelerometer device 52, determines a muscle chronaxia during ameasurement phase of about one to several seconds. This measurementphase comprises applying several different pulse durations to the targetmuscle in order to determine points of the curve depicted in FIG. 5. Bymathematical curve fitting, the value of chronaxia can be determined.This function is preferably implemented at the start of the program by ashort sequence during which measurements are taken. Once the test hasbeen completed, the primary stimulation program can start.

Referring to FIG. 5 in conjunction with FIGS. 1-3, MI sensor system 50in cooperation with device 12 and control system 40 is able to measure,through a short initial test, the chronaxia of the motomeurons of thetarget stimulated muscle. Device 12 then automatically adjusts the pulsewidth equal to the measured chronaxia. Above excitation curve 102depicted in FIG. 5, a muscle reaction is initiated, which can bedetected by sensor system 50. Because the intensity is not a reliablecurrent output scale when the impulse width varies from muscle to muscleor from one session of stimulation to another, control system 40 of theinvention uses an energy scale instead of an intensity scale.

Referring to FIG. 6, a progression of the stimulation energy 110 islinear, producing a more comfortable stimulation as realized by a user.Stimulation energy 110 can be expressed as E according to the followingequation in one embodiment:

E=RI²t,

in which R is a resistance of target muscle tissue expressed in Ohms; Iis a stimulation current expressed in milliamps; and t is a pulseduration expressed in seconds. The stimulation force, F, can then beexpressed as follows:

F=zRI²t,

wherein z is a constant. Thus:

F˜E

F varies linearly with E but not with I.

In operation, the energy output is adjustable by a user in terms of apercentage of the maximum energy output. This new scale of power outputadditionally has an advantage compared to the intensity or quantity ofelectrical charges. The practical advantage is that the strength of thecontraction brought about by the stimulation has a linear relationshipwith the energy, as depicted in FIG. 6. As a result, the user hassmoother and safer control of the contraction by acting through anenergy scale that corresponds to a physiological response. The user, oran operator, can adjust the energy scale to a desired setting in orderto achieve the desired level of contraction strength. In one embodiment,the operator defines an available energy scale and may or may notprovide the user with fine adjust within that available scale. Becausedevice 12 is a current generator, control system 40 and microcontroller46 control the electrical intensity output adjustment according to themathematical relationship between energy and intensity. In other words,the operator or, if permitted by the operator, the user to apredetermined degree, can set a desired energy level of stimulation andthe microprocessor translates this demand as a variation of intensity.

In one embodiment, the energy scale has approximately 1000 levels, orsteps, with settings running from step zero to step 999. The pulse widthand the intensity are determined for each energy step, wherein each stepcan have slight pulse width variations during energy level variations.The maximum stimulation energy, Max E, during an electrical pulse is:

Max E=(Max I)²* Max W

wherein Max I is the maximum current and W is the pulse width. In oneembodiment of system 10, the Max I is approximately 120 milliamps (mA),Max W is approximately 400 microseconds (μ,s) and the resulting Max Eis:

(120)²*400=5,760,000mA²*μs.

If system 10 has 1000 energy steps, each step represents one thousandthof the maximum energy, Max E. In one embodiment in which system 10 hasan automatic ramp, the energy variation will be linear from step tostep, using as many energy levels as possible. In another embodiment, auser can self-adjust the stimulation level, wherein each increaserequested by a user via input portion 24 results in a one energy levelincrease within a first range of step 0 to about step 99. In a secondrange from about step 100 to about step 999, each increase requested bya user produces an energy level increase according to the followingequation:

${{New}\mspace{14mu} {Level}} = {{{Old}\mspace{14mu} {Level}} + \frac{{Old}\mspace{14mu} {Level}}{64}}$

This results in the curve of FIG. 7.

When a desired energy level to be set is known, the current intensitycan be adjusted to achieve the desired level. The corresponding currentis then:

${I = \sqrt{\frac{{Max}\mspace{14mu} E}{W_{0}} \cdot \frac{{Energy}\mspace{14mu} {Level}}{1000}}},$

wherein W₀is an uncorrected pulse width. The variations of the intensityoutput preferably have about a half milliamp (mA) of minimum sensitivityadjustment. This minimum intensity adjustment is not precise enough,however, to provide an energy scale of 1000 steps. For example, if thecalculated intensity for the desired energy setting according to thepreceding equation is I=87.6586 mA, the real intensity output would beI_(corrected)=about 87.5 mA rounded to the nearest 0.5 mA value. Suchintensity inaccuracy would be responsible for any difference between thedesired energy and the real energy output.

In order to solve the problem and retain the full preciseness of theintended 1000 steps of the energy scale, microcontroller 46 calculates apulse width correction according to the following equation:

$W_{Corrected} = {\frac{{Energy}\mspace{14mu} {Level}}{1000} \cdot \frac{{Max}\mspace{14mu} E}{I_{Corrected}^{2}}}$

Slight pulse width adjustments therefore compensate the half by halfmilliamp current output adjustment in order to provide the user oroperator with a more precise energy scale of 1000 steps. In general, thedifference between WO and WCorrected will be minimal, except at very lowenergy levels and approaching a maximum current. By way of furtherexample, FIG. 8 shows an evolution of current, I, and FIG. 9 shows anevolution of pulse width, W, for each step increase request, each at anuncorrected pulse width of W=300 μs.

In another exemplary embodiment, the maximum current output of device 12is approximately 120 mA and the maximum pulse width is approximately4000. If the measured chronaxia from sensor 50 is, for example, about2000 and the current output is at a maximum of about 120 mA, the maximumenergy power of device 12 is not yet reached. In most instances, usersdo not need to use an energy higher than the one provided with the 120mAmp, but some operators, particularly trainers and medical personnelworking with professional athletes or other high performance users,would prefer to have access to the full device power for some specifictrainings. Stimulator system 10 of the invention gives the operator or,if permitted by the operator, the user to a predetermined degree, theoption of overriding the energy provided with the maximum intensitythrough an increase of the pulse width when it is not yet at the maximumof about 400 μS.

MI-Action

The MI-action mode is a work mode in which a voluntary muscularcontraction is automatically accompanied by a contraction caused byelectro-stimulation. The electro- stimulation contraction is thereforecontrolled and the working session becomes more comfortable (from boththe psychological and muscular standpoints), more intensive (the muscleworks more and in greater depth), and more complete (improvement ofcoordination). The MI-action mode allows the user to start the muscularcontraction phase by voluntarily contracting the stimulated muscle,thereby offering an opportunity to associate voluntary work withstimulation.

In operation, accelerometer 52, as part of MI sensor system 50, sensesmuscle twitches that are elicited by brief electrical test pulses duringthe resting phases. As soon as the twitch signal is modified or alteredas detected by MI sensor 50 by the voluntary contraction, device 12sends a stimulation signal to the muscle such that a voluntarycontraction and an electrical stimulation occur simultaneously. The usercan thus start the electrical muscle contraction at his or herconvenience by triggering its onset with a voluntary muscle contraction.Further, the simultaneous voluntary contraction and electricalstimulation improve training efficiency by increasing the number ofmuscle fibres that are activated.

The voluntary start of a contraction during an active rest phase ispossible within a given time span that varies depending on thestimulation treatment program used. In one embodiment, an alteration ofsound signals from output portion 23 delimits this time span as follows:

An initial sound signal of increasingly close alerts indicates that thestart of the voluntary contraction phase is possible.

A continuous sound signal indicates that it is the ideal time to startthe voluntary contraction phase.

A decreased sound signal indicates that start is still possible and thework rate is still satisfactory.

After a certain time, which varies depending on the program, duringwhich the alerts are more spaced out, the device automatically goes intothe “Pause” mode if no contraction phase has been started.

The MI-action mode is thus a bridge between voluntary workout andelectro-stimulation with a goal of increasing training efficiency.

MI-TENS

TENS is an analgesic stimulation technique in which only the sensorynerves are excited and not the motor nerves. During pain managementtreatment in MI-TENS mode, the onset of a muscle contraction is anunwanted affect that appears when intensity is raised above a particularlevel. In order to obtain an efficient TENS treatment, however, theintensity should be set as high as possible yet remain below thethreshold of motor nerve excitation, which results in musclecontraction.

MI-TENS is a feature preventing the onset of muscle contractionautomatically. On the basis of the measurements taken regularly duringthe session by sensor system 50, device 12 automatically readjusts thestimulation energy to avoid an onset of muscular contraction.Accelerometer 52 and MI sensor 50 sense muscle twitches that areelicited by brief electrical test pulses during the MI-TENS treatment.When a muscle contraction occurs, MI sensor 50 detects an onset of thetwitch response to the test pulse. This event indicates that the musclecontraction has occurred. Accordingly, control system 40 automaticallyreduces the stimulation intensity, or energy, down to a level where thetwitches are no longer detected, meaning that the contraction hasdisappeared. In other words, the MI-TENS is a supervisor that preventsthe user from increasing energy to a level where counter-indicatedmuscle contraction occurs.

MI-Range

The MI-range function indicates the ideal energy adjustment range forthe low frequency stimulation programs, for example analgesic,rehabilitative, and vascular muscle electrostimulation programs, inwhich muscle twitches are required to increase blood flow to aparticular area. Using MI-range, a user no longer needs to questionwhether the energy applied is too high or too low as this functionprovides the necessary information, thus optimising the efficiency oftreatment.

The MI-range function indicates the ideal energy adjustment range for aprogram whose efficiency requires vigorous muscular twitches and istherefore accessible only for stimulation treatment programs using lowstimulation frequencies, generally those less than about 10 Hertz in oneembodiment. In programs permitting the use of the MI-range function,stimulator device 12 checks whether a user is currently in the idealenergy range. In one embodiment, if the user is below the range,stimulator device 12 prompts the user to increase the energy bydisplaying “+” signs or another indicator prompt on display 22 or anaudible prompt via input portion 24. Once stimulator device 12 andsensor system 50 have detected the user-ideal adjustment range bydetecting at least one user physiological characteristic, a bracket orsimilar indicator appears adjacent the bar chart on display 22 ofchannel 28 to which sensor system 50 is connected. This bracketindicates the energy range within which the user should work for optimalstimulation. If the user adjusts the stimulation energy below the idealtreatment range, stimulator device 12 prompts the user to increase itagain with an audio and/or visual indicator, for example a continuousdisplay of blinking “+” signs on display 22, an audible tone, acombination of visual and audible prompts, or the like. Thus, in theMI-range function, device 12 detects the muscle twitches and recommendsa range for effectiveness suited for a user's individual physiologicalcharacteristics.

Energy Level Setting Assistance

The energy level setting assistance (ELSA) function provides feedback toa user under stimulation, and/or to an operator monitoring stimulation,regarding the degree of muscle work associated with the currentstimulation parameters, based on detected user physiologicalcharacteristics and muscle response. Sensor system 50 measures thedegree of muscular response and control system 40 determines thepercentage of muscular fibres that are recruited, or active, versusthose that are inactive. The ELSA function thus informs the user whetherhe or she needs to further increase intensity of stimulation or if anincrease would not be beneficial because all muscle fibres are alreadyactive, allowing the user and/or operator to measure the degree ofmuscle workout.

Potentiation

Potentiation of a muscle is reached during a warm-up phase, which canvary according to user physiology. The muscle can be prepared for theeffort to come by applying a few brief muscle contractions prior to thereal exercise. This phenomenon is called potentiation. More precisely,for one action potential the twitch force is more intense once themuscle is fully potentiated. As a consequence, the maximum force can bereached more rapidly with less action potential involved. This effectcan be elicited using electrosimulation and is frequently used forathletes in sports in which quick reactions and/or explosive efforts arerequired, for example power-lifting, sprinting, and the like. Thus, inPotentiation mode, MI sensor system 50 can detect when a muscle is fullypotentiated by measuring the increase in the muscle response to appliedstimulation pulses.

Cramp Prevention

One common problem associated with muscle stimulation is the control ofmuscle cramps. It is well known that a muscle is much more likely tocramp after an effort in which the muscle has been extensively exerted.After intense efforts, electro-stimulation can be used to relax themusculature and increase blood flow in an active recovery treatment. Theonset of muscle cramps during the recovery phase is painful and needs tobe avoided. MI-sensor 50 and control system 40 can therefore also beused to detect the onset of muscle cramping by detecting changes in themuscle twitches due to unwanted muscle contractions.

MI-Fatigue

The measurement of a degree of muscular fatigue is an indication to auser of an electro- stimulation device that there will be little or nobenefit obtained from continuing muscle stimulation during a particulartreatment session. In one embodiment, the detection of muscle fatigue isbased upon a measurement of a shift in fusion frequency. As depicted inFIG. 10, fusion occurs when the individual mechanical responses (graphB) to the electrical excitation pulses (graph A) can no longer bedifferentiated in the muscle (graph C). It is known that the fusionfrequency decreases when fatigue increases due to a longer relaxationtime in the individual mechanical responses, shown as the dotted curvein graph B.

The system 10 of the present invention detects the fusion frequencyvalue by measuring the reaction of the target muscle to an applied scanin excitation frequencies. In other words, the period T in graph A ofFIG. 10 is progressively decreased by device 12 and control system 40until sensor(s) 50 are unable to detect any further mechanical responsein the muscle. This indicates fusion as depicted in graph C. Thismeasurement is preferably carried out first, at the beginning of atreatment session, and can be repeated throughout theelectro-stimulation program. Once the successive fusion frequencies havedecreased to a certain percentage of the initial value, the user knowsthat his or her muscle has reached a particular level of fatigue, asillustrated in graph D of FIG. 10. The level of muscle fatigue can thusbe measured and displayed in real time by electro-stimulation system 10.

In use, one embodiment of stimulation system 10 delivers a musclestimulation signal to a target tissue of a user as described above byelectrode assembly 16. The muscle stimulation signal will typically beone of a plurality of stimulation signals delivered to the target tissueof the user as part of a muscle stimulation treatment program selectedand/or customized by an operator or user. Accordingly, one embodiment ofsystem I 0 is adapted to accept a first set of input data andinformation from the user relating to treatment goals, status, andcharacteristics, and a second set of data and information from anoperator. The second set can include maximum and minimum treatmentprogram settings, available treatment programs, and other informationrelated to a user's treatment, goals, and use of system 10. Electrodeassembly 16 and sensor system 50 then detect a muscle response to thestimulation signal, wherein the response can be one or a plurality ofreaction pulses.

Sensor system 50 and control system 40 automatically diagnose at leastone characteristic of the target tissue from the detected muscleresponse. In one embodiment, the automatic diagnosis includescalculating a coefficient of correlation of a plurality of detectedreaction pulses. The at least one characteristic diagnosed can be aphysiological characteristic of the user, a muscle chronaxia, a fatiguelevel of a target muscle, or another characteristic related to musclecondition, performance, or reaction. Upon diagnosis, system 10 adjustsone or more parameters of the muscles stimulation signal and treatmentprogram and subsequently delivers an adjusted muscle stimulation signalto a target tissue of a user.

During use, one embodiment of system 10 provides diagnostic, status, andtreatment data as output. System 10 can be programmed to provide a firstlevel of real time diagnostic and treatment data to the user and asecond level of real time diagnostic and treatment data to an operator.The second level of data can include the first level of data provided tothe user, in addition to more particular status, treatment, and usagedata and information of interest to medical professionals, trainers, andother operators.

The adaptive muscle stimulation system and method of the inventiontherefore provide a compact electro-stimulation device that can operatein a plurality of modes to adapt to an individual user's physiology,target muscle group, and desired treatment mode. In particular treatmentmodes, the stimulation device can monitor a treatment session andprovide appropriate feedback to a user based upon delivered stimulationand detected muscle feedback and response. The stimulation device cantherefore be used safely and effectively by non-medical personnel fortraining and therapeutic applications while still providing the completeand advanced treatment modes and options required by medicalprofessionals and certified trainers.

The invention may be embodied in other specific forms without departingfrom the spirit of the essential attributes thereof; therefore theillustrated embodiment should be considered in all respects asillustrative and not restrictive, reference being made to the appendedclaims rather than to the foregoing description to indicate the scope ofthe invention.

1. (canceled)
 2. A stimulation system for automatically supplementing avoluntary muscle contraction with a muscle contraction caused byelectrical stimulation, the system comprising: an electrode assemblyincluding at least one electrode configured to deliver electricalstimulation signals to a muscle of a user; a sensor configured to detectcontractions of the muscle; and a control system operably connected tothe electrode assembly and the sensor, the control system configured to:detect, with the sensor, a voluntary contraction of the muscle, andresponsive to detecting the voluntary contraction of the muscle, send anelectrical stimulation signal through the at least one electrode to themuscle, the electrical stimulation signal configured to cause the muscleto contract.
 3. The system of claim 2, wherein the control system isconfigured to detect a voluntary contraction by: sending an electricaltest pulse through the at least one electrode to the muscle, theelectrical test pulse configured to cause a muscle twitch; detecting,with the sensor, a first signal indicative of the muscle twitch causedby the electrical test pulse; and detecting, with the sensor, a secondsignal different from the first signal, the second signal indicating avoluntary muscle contraction.
 4. The system of claim 3, wherein thecontrol system is configured to send the electrical test pulse in aresting phase between voluntary contractions of the muscle.
 5. Thesystem of claim 2, wherein the sensor is an accelerometer.
 6. The systemof claim 5, wherein the accelerometer is operable to detect an onset, amodification, or a disappearance of the muscle contraction.
 7. Thesystem of claim 2, wherein the sensor comprises a plurality ofaccelerometers.
 8. The system of claim 2, wherein the sensor is atension strain gauge.
 9. The system of claim 2, further comprising aspeaker connected to the control system, and wherein the control systemis further configured to provide an auditory signal, with the speaker,to indicate a start of a voluntary contraction phase.
 10. The system ofclaim 2, wherein the control system is configured to enter a pause modeif no voluntary contraction is detected during a predetermined period.11. The system of claim 2, wherein the control system is adapted tostore at least one preprogrammed electrostimulation program.
 12. Thesystem of claim 11, wherein the preprogrammed electrostimulation programis selected from a program group consisting of a muscle fitnesselectrostimulation program, a muscle aesthetic electrostimulationprogram, a sport training electrostimulation program, a pain managementelectrostimulation program, a muscle rehabilitation electrostimulationprogram, and a vascular electrostimulation program.
 13. A method forautomatically supplementing a voluntary muscle contraction with a musclecontraction caused by electrical stimulation, the method comprising:monitoring a muscle of a user for a voluntary muscle contraction;detecting the voluntary muscle contraction of the muscle; and responsiveto detecting the voluntary contraction of the muscle, sending anelectrical stimulation signal through an electrode to the muscle, theelectrical stimulation signal configured to cause the muscle tocontract.
 14. The method of claim 13, wherein monitoring a muscle of auser for a voluntary contraction comprises: delivering an electricaltest pulse to the muscle through the electrode, the electrical testpulse configured to cause a muscle twitch; and detecting a first signalindicative of the muscle twitch with a sensor.
 15. The method of claim14, wherein detecting the voluntary muscle contraction of the musclefurther comprises detecting a second signal different than the firstsignal.
 16. The method of claim 13, further comprising applying at leastone electrode to the user, the at least one electrode configured todeliver the electrical stimulation signal to the muscle.
 17. The methodof claim 13, further comprising applying at least one sensor to theuser, the at least one sensor configured to detect a contraction of themuscle.
 18. The method of claim 17, wherein the at least one sensorcomprises an accelerometer.
 19. The method of claim 13, furthercomprising delivering a preprogrammed electrostimulation program to themuscle.
 20. The method of claim 19, wherein the preprogramedelectrostimulation program is selected from a program group consistingof a muscle fitness electrostimulation program, a muscle aestheticelectrostimulation program, a sport training electrostimulation program,a pain management electrostimulation program, a muscle rehabilitationelectrostimulation program, and a vascular electrostimulation program.21. A stimulation system comprising: a means for delivering anelectrical stimulation signal to a muscle of a user; a means fordetecting contractions of the muscle; and a control means operablyconnected to the means for delivering and the means for detecting, thecontrol means configured to: detect, with the means for detecting, avoluntary contraction of the muscle, and responsive to detecting avoluntary contraction of the muscle, send an electrical stimulationsignal through the means for delivering to the muscle, the electricalstimulation signal configured to cause the muscle to contract.